Blue moon to grace our skies tonight; next one won’t happen until 2015!

View of a full moon taken by NASA's Expedition 10 crew who had been orbiting Earth aboard the International Space Station between 2004 and 2005. Credit: NASA

It seems to be a fitting celestial tribute to the late astronaut Neil Armstrong, whose memorial service takes place today in Ohio, as there’s going to be a rare phenomenon in our skies tonight – a blue moon. That’s because, for the second time this August, there will be a full moon.

And it will be July 2015 before two full moons are set to occur again in one calendar month, with the name blue moon having carried on from folklore to represent a rare event.

This month, the first full moon occurred on the night of 1/2 August before tonight’s full moon right on the cusp of the start of September.

Blue in name only?

However, the term blue moon generally only applies to the name that has been given to this celestial phenomenon, so one is not likely to glimpse a moon that’s blue in colour at sunset tonight.

But, you never know …

According to NASA’s Dr Tony Phillips, on rare occasions people have witnessed a blue moon. For this to happen though, you need to add a volcanic eruption to the mix. In 1183, for instance, Phillips writes on Science.nasa.gov about how people saw blue moons after the Indonesian volcano Krakatoa exploded, and again in 1983 after the eruption of the El Chichon volcano in Mexico.

Apparently the plumes of ash that blast out into the atmosphere after such volcanic eruptions carry particles that are almost the same wavelength as red light. And the result? This particles scatter red light that allow blue light to pass through, acting like a blue filter so that the moon appears to be blue …

And, according to Phillips some forest fires can also have the same blue effect.

Tom King from Watauga in Texas took this image of a blue moon on the night of 13 October 2003. "The moon began rising in the east with a strange blue tint I had not seen before … The temperature was falling and the air was damp and heavy with moisture," wrote King on Spaceweather.com

Every two to three years there’s an extra full moon in a month, so if you don’t want to wait until July 2015, cast your eyes upwards tonight!

The late Neil Armstrong, pictured stepping onto the surface of the moon on 21 July 1969. Credit: NASA

As for the first person to ever walk on the moon, a memorial service is taking place in Ohio today for the late astronaut Neil Armstrong, who made history when he set foot on the moon during NASA’s Apollo 11 mission in July 1969. Armstrong passed away last Saturday at the age of 82.